KR102652923B1 - Backlight unit and display device - Google Patents

Abstract

Embodiments of the present invention relate to a backlight unit and a display device, where the duty of a light source driving signal is adjusted to avoid the frequency component that causes flicker among the frequency components of luminance that appear during a period of driving in a low-speed driving mode. By adjusting it, it is possible to prevent flicker from occurring in low-speed driving mode. Therefore, the power consumption of the display device can be reduced through the low-speed driving mode, and the efficiency of the display device can be improved by enabling low-speed driving at a lower display driving frequency.

Description

Backlight unit and display device {BACKLIGHT UNIT AND DISPLAY DEVICE}

Embodiments of the present invention relate to a backlight unit and a display device.

As the information society develops, the demand for display devices that display images is increasing, and various types of display devices such as liquid crystal display devices and organic light emitting display devices are being utilized.

Such a display device includes a display panel in which a plurality of subpixels are arranged, and can display an image by controlling the brightness of the plurality of subpixels.

Additionally, the display device may be driven in a low-speed drive mode according to the displayed image to reduce power consumption. For example, it may be driven in a low-speed drive mode in AoD (Always on Display) mode, which displays only specific information in some areas of the display panel.

At this time, as the display device is driven at a low display driving frequency, the length of the data retention period in one frame period may become longer, and as a result, the extent to which luminance is reduced in one frame period may increase. Additionally, flicker may be recognized due to an increase in luminance deviation between frames, resulting in many difficulties in implementing a low-speed driving mode.

An object of embodiments of the present invention is to provide a display device that can prevent flicker from being recognized in an image displayed by a display panel during a period of driving in a low-speed driving mode.

The purpose of embodiments of the present invention is to provide a backlight unit and a driving method thereof that can prevent flicker recognition in a low-speed driving mode.

In one aspect, embodiments of the present invention include a display panel, a backlight unit that includes a plurality of light sources and supplies light to the display panel, and a driving circuit that drives the plurality of light sources, and the driving circuit includes a display panel. During the driving period in this low-speed driving mode, at least one first light source driving signal and at least one second light source driving signal are output in one frame period, and the first light source driving signal and the second light source driving signal have frequency and duty and an amplitude is different.

In another aspect, embodiments of the present invention include a display panel, a backlight unit that supplies light to the display panel, and a plurality of light sources included in the backlight unit, wherein at least one of the plurality of light sources is a first driving unit. A display device in which the driving frequency, the ratio of the emission period, the emission luminance level, and the emission start timing are constant in the second driving mode, and at least one of the driving frequency, the ratio of the emission period, the emission luminance level, and the emission start timing are variable in the second driving mode. to provide.

In another aspect, embodiments of the present invention provide a backlight unit including a plurality of light sources, wherein at least one of the plurality of light sources has a driving frequency, a ratio of the light emission period, a light emission luminance level, and a light emission start in a first driving mode. A backlight unit is provided in which timing is constant and at least one of a driving frequency, a ratio of a light emission period, a light emission luminance level, and a light emission start timing is variable in a second drive mode.

According to embodiments of the present invention, by varying the light source driving signal that controls the driving of the light source included in the backlight unit in the low-speed driving mode, the frequency component that allows flicker to be recognized among the frequency components of luminance that appears in one frame period is changed. enable it to be reduced.

Accordingly, flicker is prevented from being recognized in the low-speed driving mode, and the use efficiency of the display device can be improved by reducing power consumption by the low-speed driving mode.

1 is a diagram showing the schematic configuration of a display device according to embodiments of the present invention.
2A and 2B are diagrams showing examples of luminance changes in a normal driving mode and a low-speed driving mode of a display device according to embodiments of the present invention.
Figures 3 and 4 are diagrams illustrating an example of a method for improving flicker through analysis of the frequency component of luminance that appears in one frame period in a low-speed driving mode of a display device according to embodiments of the present invention.
5A to 5D are diagrams illustrating examples of backlight unit driving signals in a normal driving mode and a low-speed driving mode of a display device according to embodiments of the present invention.
Figure 6 is a diagram showing an example of a configuration for generating and outputting a driving signal of a backlight unit in a display device according to embodiments of the present invention.
7 to 10 are diagrams showing examples of driving signals of a backlight unit when the backlight unit is edge-type according to embodiments of the present invention.
11 and 12 are diagrams showing examples of driving signals of the backlight unit when the backlight unit is a direct type according to embodiments of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to the exemplary drawings. In adding reference numerals to components in each drawing, identical components may have the same reference numerals as much as possible even if they are shown in different drawings. Additionally, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description may be omitted.

Additionally, when describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the essence, sequence, order, or number of the components are not limited by the term. When a component is described as being “connected,” “coupled,” or “connected” to another component, that component may be directly connected or connected to that other component, but there are no other components between each component. It should be understood that may be “interposed” or that each component may be “connected,” “combined,” or “connected” through other components.

Figure 1 is a diagram showing the schematic configuration of a display device 100 according to embodiments of the present invention.

Referring to FIG. 1, a display device 100 according to embodiments of the present invention includes a display panel 110 including an active area (A/A) and a non-active area (N/A), and a display panel. It may include a gate driving circuit 120, a data driving circuit 130, and a controller 140 for driving 110.

In the display panel 110, a plurality of gate lines (GL) and a plurality of data lines (DL) are arranged, and a subpixel (SP) is arranged in an area where the gate line (GL) and the data line (DL) intersect. .

The gate driving circuit 120 is controlled by the controller 140 and sequentially outputs scan signals to the plurality of gate lines GL disposed on the display panel 110 to determine the driving timing of the plurality of subpixels SP. control.

The gate driving circuit 120 may include one or more gate driver integrated circuits (GDIC, Gate Driver Integrated Circuit) and may be located on only one side or both sides of the display panel 110 depending on the driving method. It may be possible.

Each gate driver integrated circuit (GDIC) is connected to a bonding pad of the display panel 110 using a Tape Automated Bonding (TAB) method or a Chip On Glass (COG) method, or is connected to a bonding pad of the display panel 110 using a Tape Automated Bonding (TAB) method or a Chip On Glass (COG) method. It may be implemented as an In Panel type and placed directly on the display panel 110, and in some cases, it may be integrated and placed on the display panel 110. Additionally, each gate driver integrated circuit (GDIC) may be implemented using a chip on film (COF) method mounted on a film connected to the display panel 110.

The data driving circuit 130 receives image data from the controller 140 and converts the image data into an analog data voltage. Then, the data voltage is output to each data line (DL) in accordance with the timing when the scan signal is applied through the gate line (GL), so that each subpixel (SP) expresses brightness according to the image data.

The data driving circuit 130 may include one or more source driver integrated circuits (SDIC).

Each source driver integrated circuit (SDIC) may include a shift register, a latch circuit, a digital-to-analog converter, an output buffer, etc.

Each source driver integrated circuit (SDIC) may be connected to a bonding pad of the display panel 110 using a tape automated bonding (TAB) method or a chip-on-glass (COG) method, or may be placed directly on the display panel 110. , depending on the case, may be integrated and placed on the display panel 110. Additionally, each source driver integrated circuit (SDIC) may be implemented in a chip-on-film (COF) method. In this case, each source driver integrated circuit (SDIC) is mounted on a film connected to the display panel 110 and , may be electrically connected to the display panel 110 through wires on the film.

The controller 140 supplies various control signals to the gate driving circuit 120 and the data driving circuit 130, and controls the operations of the gate driving circuit 120 and the data driving circuit 130.

The controller 140 may be mounted on a printed circuit board, a flexible printed circuit, etc., and be electrically connected to the gate driving circuit 120 and the data driving circuit 130 through a printed circuit board, a flexible printed circuit, etc. .

The controller 140 causes the gate driving circuit 120 to output a scan signal according to the timing implemented in each frame, and converts the externally received image data to fit the data signal format used by the data driving circuit 130. The converted image data is output to the data driving circuit 130.

The controller 140 externally sends various timing signals including a vertical synchronization signal (VSYNC), a horizontal synchronization signal (HSYNC), an input data enable signal (DE, Data Enable), and a clock signal (CLK) along with video data. Receive from (e.g. host system).

The controller 140 may generate various control signals using various timing signals received from the outside and output them to the gate driving circuit 120 and the data driving circuit 130.

As an example, the controller 140 uses a gate start pulse (GSP, Gate Start Pulse), a gate shift clock (GSC), and a gate output enable signal (GOE, Outputs various gate control signals (GCS) including Gate Output Enable.

Here, the gate start pulse (GSP) controls the operation start timing of one or more gate driver integrated circuits (GDIC) constituting the gate driving circuit 120. The gate shift clock (GSC) is a clock signal commonly input to one or more gate driver integrated circuits (GDIC), and controls the shift timing of the scan signal. The gate output enable signal (GOE) specifies timing information for one or more gate driver integrated circuits (GDIC).

In addition, the controller 140 uses a source start pulse (SSP), a source sampling clock (SSC), and a source output enable signal (SOE) to control the data driving circuit 130. Outputs various data control signals (DCS) including Output Enable.

Here, the source start pulse (SSP) controls the data sampling start timing of one or more source driver integrated circuits (SDICs) constituting the data driving circuit 130. The source sampling clock (SSC) is a clock signal that controls the sampling timing of data in each source driver integrated circuit (SDIC). The source output enable signal (SOE) controls the output timing of the data driving circuit 130.

This display device 100 supplies various voltages or currents to the display panel 110, the gate driving circuit 120, the data driving circuit 130, etc., or has a power management integrated circuit that controls the various voltages or currents to be supplied. More may be included.

Each subpixel (SP) is defined by the intersection of the gate line (GL) and the data line (DL), and depending on the type of display device 100, liquid crystal or light emitting elements may be disposed.

For example, when the display device 100 is a liquid crystal display device, it includes a light source device such as a backlight unit that irradiates light to the display panel 110, and liquid crystal is disposed in the subpixel (SP) of the display panel 110. do. Also, by adjusting the arrangement of the liquid crystals by the electric field formed as the data voltage is applied to each subpixel (SP), an image can be displayed with brightness according to the image data.

Here, the backlight unit may be disposed below the display panel 110 and supply light to the display panel 110. This backlight unit may be driven by a pulse width modulation signal to reduce power consumption, and the light source included in the backlight unit may be repeatedly turned on and off at regular intervals.

Additionally, in order to reduce power consumption of the display device 100, the display device 100 may be driven in a normal driving mode and a low-speed driving mode, depending on the case.

FIGS. 2A and 2B are diagrams showing examples of luminance changes in a normal driving mode and a low-speed driving mode of the display device 100 according to embodiments of the present invention.

Referring to FIG. 2A, the display device 100 may be driven in a normal driving mode (or first driving mode) at, for example, a display driving frequency of 60 Hz. Accordingly, the data voltage Vdata may be supplied to each subpixel SP disposed on the display panel 110 during a frame period corresponding to 60 Hz in accordance with the synchronization signal SYNC of 60 Hz.

Here, the example shown in FIG. 2A shows a case where the polarity of the data voltage (Vdata) is inverted for each frame and supplied to prevent deterioration due to tilting of the liquid crystal.

In addition, each subpixel (SP) displays brightness corresponding to the voltage difference between the pixel voltage (Vpxl) and the common electrode (Vcom) according to the data voltage (Vdata), allowing the display panel 110 to display an image. .

At this time, the pixel voltage (Vpxl) applied to the pixel electrode during one frame period may decrease, but since the frame period is short, the decrease in luminance due to the decrease in pixel voltage (Vpxl) may not be recognized.

On the other hand, when the display device 100 is driven in a low-speed driving mode, such a decrease in luminance may be perceived as the length of one frame period increases.

Referring to FIG. 2B, the display device 100 may be driven in a low-speed driving mode (or a second driving mode) at a display driving frequency within the range of 1 Hz to 30 Hz, for example. Accordingly, the data voltage Vdata can be supplied to each subpixel SP during a frame period corresponding to 1 Hz to 30 Hz.

Here, since one frame period becomes longer in the low-speed driving mode, the amount of decrease in the pixel voltage (Vpxl) during one frame period may increase.

Accordingly, the extent of luminance degradation may increase due to a decrease in pixel voltage (Vpxl), and flicker may be recognized in low-speed driving mode due to luminance deviation between frames due to this luminance decrease.

Also, in the low-speed driving mode, the luminance of an image in which flicker is recognized may have a large amplitude of a specific frequency component.

That is, flicker recognized in low-speed driving mode may appear as luminance decreases during one frame period, but flicker may also be recognized according to the frequency component of luminance that appears during one frame period.

Embodiments of the present invention provide a method for preventing flicker from being recognized in a low-speed driving mode by analyzing the frequency component of luminance that appears during one frame period in the low-speed driving mode.

Figures 3 and 4 are diagrams illustrating an example of a method for improving flicker through analysis of the frequency component of luminance that appears in one frame period in a low-speed driving mode of the display device 100 according to embodiments of the present invention.

Referring to FIG. 3, the display device 100 may be driven in a low-speed driving mode, for example, at a display driving frequency of 20Hz. Therefore, as one frame period becomes longer than the frame period of the normal driving mode, the extent to which luminance deteriorates during one frame period may increase.

Here, if the frequency component of the output signal measured by a photodiode is analyzed for luminance during one frame period in the low-speed driving mode, frequency components may appear in the 20Hz, 40Hz, and 60Hz bands, for example. In particular, the amplitude of the frequency component may be largest at 20Hz, which is the display driving frequency band.

At this time, by adjusting the driving signal of the backlight unit that supplies light to the display panel 110, that is, the signal that controls the turn-on and turn-off of the light source included in the backlight unit, the frequency of luminance appearing during one frame period The frequency component in the 20Hz band may be reduced.

For example, by varying at least one of the frequency, duty (or pulse width), amplitude, and delay period of the driving signal of the backlight unit during one frame period, the frequency component of luminance appearing in the frame period can be adjusted.

That is, the frequency component of the luminance displayed by the display panel 110 in the low-speed driving mode by varying at least one of the driving frequency of the light source included in the backlight unit, the ratio of the light emission period, the light emission luminance level, and the light emission start timing. This can be changed.

To be described in detail with reference to FIG. 4, based on a waveform (saw tooth pulse) similar to luminance that appears during the frame period of the low-speed drive mode and the driving signal of the backlight unit, a modulated signal (Modulated Signal), that is, the backlight unit The luminance waveform that appears according to the driving signal can be obtained.

Here, the driving signal of the backlight unit may be an aperiodic signal with different duties. The driving signal of the backlight unit is divided into signals with the same period, and based on the driving signal of the divided backlight unit and a waveform similar to the luminance that appears during the frame period of the low-speed driving mode, modulation is performed according to the driving signal of the divided backlight unit. signal can be obtained.

When each of these modulated signals is Fourier transformed, they may appear as frequency components with different amplitudes and phases.

In other words, as the delay period (D1, D2, D3, D4, D5) or duty (W1, W2, W3, W4, W5) of the driving signal of the backlight unit is different, the frequency of luminance by each driving signal of the backlight unit is different. Ingredients may appear differently.

And, when modulated signals having different frequency components are added together, specific frequency components may be canceled out and reduced.

Accordingly, the frequency component of luminance that appears during one frame period in the low-speed driving mode can be adjusted by varying the duty of the driving signal of the backlight unit during one frame period.

Additionally, by varying the driving signal of the backlight unit so that the specific frequency component can be reduced, the luminance that appears in the low-speed driving mode can avoid the specific frequency component, thereby preventing flicker according to the specific frequency component from being recognized.

That is, by varying at least one of the frequency, duty, amplitude, and delay period of the driving signal supplied to the light source included in the backlight unit during one frame period of the low-speed driving mode, the frequency component of the luminance that appears during one frame period of the low-speed driving mode This can be adjusted.

FIGS. 5A to 5D illustrate examples of backlight unit driving signals in a normal driving mode and a low-speed driving mode of the display device 100 according to embodiments of the present invention.

Referring to FIG. 5A, in the normal driving mode, the driving signal of the backlight unit may have a constant frequency F, duty W, amplitude A, and delay period D during one frame period. In this general driving mode, the frequency of the driving signal of the backlight unit may be in the kHz band.

That is, in the normal driving mode, the light source included in the backlight unit may be turned on and off at the same cycle during one frame period. Also, in each cycle, the ratio of the light emission period may be constant and the level of light emission luminance may be constant. Additionally, the timing at which light emission starts in each frame period may be the same.

As such, in the normal driving mode, the driving signal of the backlight unit is constantly applied, so that the light source included in the backlight unit can be driven to periodically exhibit constant luminance. That is, in the normal driving mode, the duty of the driving signal of the backlight unit can be determined to be constant in order to reduce power consumption or adjust the overall luminance level.

And, referring to FIG. 5B, in the low-speed driving mode, the driving signal of the backlight unit may vary in at least one of frequency, duty, and amplitude during one frame period.

For example, in the first subframe (or section) period of one frame period, the frequency of the driving signal of the backlight unit may be F1, the pulse width may be W1, and the amplitude may be A1.

Additionally, the frequency of the driving signal of the backlight unit in the second subframe period is F2, the pulse width is W2, and the amplitude is A2, which may be different from the driving signal supplied in the first subframe period.

Additionally, the frequency F3, pulse width W3, and amplitude A3 of the driving signal supplied in the third subframe period may be different from the driving signal supplied in the first and second subframe periods.

Additionally, as shown in the example shown in FIG. 5B, the delay period before the driving signal is supplied in each frame period may be varied.

That is, the delay period D1 in the first frame period and the delay period D2 in the second frame period may be different.

Additionally, in some cases, as shown in the example shown in FIG. 5C, a plurality of driving signals with the same frequency, duty, and amplitude may be applied to some subframe periods among the subframe periods included in one frame period.

Accordingly, the number of driving signals supplied for each subframe period may be different.

Here, the frequency of the driving signal of the backlight unit in the low-speed driving mode may be in the Hz band. That is, the frequency may be lower than the frequency of the driving signal of the backlight unit in normal driving mode.

In addition to the above-described example, the driving signal of the backlight unit may be varied and supplied for each subframe period during one frame period in the low-speed driving mode by various methods. Accordingly, the driving frequency of the light source included in the backlight unit, the ratio of the light emission period, the light emission luminance level, etc. may vary for each subframe period. Additionally, the timing at which the light source starts emitting light may be different for each frame period.

Since the duty of the driving signal is varied and supplied for each subframe period, the frequency components of luminance appearing in the first subframe period, the second subframe period, and the third subframe period may be different. Additionally, a driving signal may be supplied so that the frequency component that causes flicker to be recognized is offset from the frequency component of luminance that appears in each subframe period.

In this way, by analyzing the frequency component of the luminance that appears during one frame period in the low-speed driving mode, the driving signal of the backlight unit is varied to reduce the frequency component that allows the flicker to be recognized, so that the flicker is not recognized in the low-speed driving mode. It can prevent this.

Additionally, by preventing flicker from being recognized in the low-speed driving mode, power consumption can be reduced through the low-speed driving mode, and the efficiency of the display device 100 can be increased by enabling driving at a lower display driving frequency.

Figure 6 is a diagram showing an example of a configuration for generating and outputting a driving signal of a backlight unit in a display device according to embodiments of the present invention.

Referring to FIG. 6, the arithmetic circuit 300 receives image data (or image patterns) from the host system 200.

The operation circuit 300 generates light source control data (PWM Data) for controlling the operation of the backlight unit based on at least one of the image data received from the host system 200 and the display driving frequency in the low-speed driving mode. .

This light source control data (PWM Data) may include information on the frequency (or subframe period), duty (or pulse width), amplitude, and delay period of the driving signal of the backlight unit.

As an example, the operation circuit 300 may generate and output light source control data (PWM Data) by referring to a lookup table in which light source control data (PWM Data) according to the driving frequency or image data of the low-speed drive mode is stored. .

For example, this operation circuit 300 may be the controller 140 included in the display device 100, may be implemented in the form of a chip inside the controller 140, or may be provided separately from the controller 140. It may be a microcontroller unit (MCU), etc.

Light source control data (PWM Data) generated by the arithmetic circuit 300 is transmitted to the driving circuit 400.

The driving circuit 400 outputs a light source driving signal (PWM) for driving the light source 500 included in the backlight unit based on the light source control data (PWM Data) received from the arithmetic circuit 300.

The light source driving signal (PWM) may be a signal whose frequency, duty, amplitude, and delay period are determined according to light source control data (PWM Data).

That is, the driving circuit 400 may output a light source driving signal (PWM) in which at least one of frequency, duty, and amplitude varies during one frame period. Additionally, a light source driving signal (PWM) with a different delay period may be output for each frame period.

This driving circuit 400 may be a light source integrated circuit (eg, LED IC) for driving the light source 500, or may be a power management integrated circuit (PMIC) or a pulse width modulation integrated circuit (PWM IC). Additionally, the driving circuit 400 may be connected to a printed circuit included in the backlight unit or may be disposed in a printed circuit connected to the display panel 110.

In this way, the light source driving signal (PWM) that drives the light source 500 included in the backlight unit in the low-speed driving mode can be applied in a variable manner during one frame period by the operation circuit 300 and the driving circuit 400. do.

Therefore, in the low-speed drive mode, the driving frequency, ratio of the light emission period, light emission luminance level, and light emission start timing of the light source 500 are varied to avoid the frequency component of the luminance that appears in the low-speed drive mode being recognized as flicker. By doing so, it is possible to improve the flicker phenomenon in low-speed driving mode.

7 to 10 are diagrams showing examples of driving signals of a backlight unit when the backlight unit is edge-type according to embodiments of the present invention.

Referring to FIGS. 7 and 8 , the light source 500 may be disposed on at least one side of the backlight unit, and FIG. 7 shows the light source 500 being disposed in the same direction as the scan direction of the display panel 110. 8 shows an example in which the light source 500 is arranged in a direction that intersects the scanning direction of the display panel 110.

As for the light source 500, a plurality of light sources 500 may be arranged in the form of one light source array 610, 620, and 630.

For example, a first light source 510, a second light source 520, a third light source 530, and a fourth light source 540 may be disposed in each of the light source arrays 610, 620, and 630.

And, the first light source 510 is driven by a light source driving signal (PWM) supplied through the first channel, and each of the second light source 520, third light source 530, and fourth light source 540 is It can be driven by a light source driving signal (PWM) supplied through the second channel, third channel, and fourth channel.

The light source driving signal (PWM) supplied through each channel in the low-speed driving mode may vary in at least one of frequency, duty, amplitude, and delay period.

That is, the length of the subframe to which the light source driving signal (PWM) is applied in one frame period, the ratio of the period in which the light source 500 is turned on in the subframe, or the voltage level that turns on the light source 500 is It can be variable. Additionally, the timing at which the light source 500 starts emitting light during a frame period may vary.

For example, as in Case 1 and Case 2, the duty of the light source driving signal (PWM) in the first subframe (SF1) may be A%. And, the duty of the light source driving signal (PWM) in the second subframe (SF2) and the third subframe (SF3) may be B% and C%, respectively.

Additionally, the amplitude of the light source driving signal (PWM) may be different in each subframe.

Here, the case where the length of each subframe is the same is shown as an example, but in some cases, the length of the subframe may also vary. Additionally, the delay period before the light source driving signal (PWM) is supplied may be different in different frame periods.

Additionally, a light source driving signal (PWM) with constant duty and amplitude may be supplied multiple times in a specific subframe period.

In this edge-type backlight unit, each channel may supply the light source driving signal (PWM) simultaneously, as in Case 1, or may supply the light source driving signal (PWM) sequentially, as in Case 2.

In this way, by adjusting the duty and amplitude of the light source driving signal (PWM) supplied in each subframe period in one frame period of the low-speed driving mode, the frequency component that causes flicker is canceled to prevent flicker in the low-speed driving mode. can prevent it from being recognized.

Meanwhile, the light source 500 driven by each channel may be disposed in each light source array 610, 620, and 630 as in the example above, but may be disposed in the same light source array 610, 620, and 630. The light source 500 may be driven by the same channel.

9 and 10, the first light source 510, the second light source 520, the third light source 530, and the fourth light source 540 disposed in the light source array 610 are transmitted through the first channel. It can be driven by a supplied light source driving signal (PWM). Additionally, the light sources 500 disposed in the light source arrays 620 and 630 may be driven by a light source driving signal (PWM) supplied through the second channel and the third channel, respectively.

Additionally, each channel may supply the light source driving signal (PWM) at the same timing, or may supply the light source driving signal (PWM) sequentially at shifted timing.

That is, flicker may occur depending on the display driving frequency in the low-speed driving mode, but may also occur depending on the image displayed by the display panel 110.

Accordingly, the light source 500 that emits light to the first area (Area1) is driven through the first channel, and the light source 500 that emits light to the second area (Area2) and the third area (Area3) respectively By driving through the second and third channels, it is possible to easily adjust the light source driving signal (PWM) according to the input image. Here, the first area (Area1), the second area (Area2), and the third area (Area3), which are areas where light is emitted from one or more light sources 500, are numbered according to the input image information. , the size and shape of the area may be set differently. For example, if the input image is divided into five areas and the light emitted must be controlled for each area, the areas where light is emitted from one or more light sources 500 may be divided into five areas of different sizes. It can be set to 1 area. In addition, the first area (Area1), the second area (Area2), and the third area (Area3), which are areas where light is emitted from one or more light sources 500, are fixed at every frame of the display or at certain frames. or may be set differently. For example, if the input image is an image that hardly changes for 30 frames, the set area may be set as a fixed area that does not change for 30 frames. Additionally, if the input image is an image that changes more than a predetermined standard every 10 frames, the set area can be set to change every 10 frames.

The light source driving signal (PWM) supplied to each channel can be varied independently. For example, as an example shown in FIG. 10, the light source driving signal (PWM) supplied to the first channel has a duty of A%, The duty can be varied as B% and C%, and the light source driving signal (PWM) supplied to the second channel can be varied as D%, E%, and F%. Additionally, the light source driving signal (PWM) supplied to the third channel can vary the duty to G%, H%, and I%.

Additionally, the amplitude of the light source driving signal (PWM) supplied through each channel during the corresponding subframe period may be different, and the length of the corresponding subframe period may also be different.

In this way, by driving the adjacently placed light sources 500 through the same channel and supplying a light source driving signal (PWM) with different duty, amplitude, etc. for each channel, the light source driving signal (PWM) is generated in the edge-type backlight unit. The flicker improvement effect can be improved by adjusting .

And, in some cases, the channels that control each light source 500 included in the edge-type backlight unit can be driven independently, thereby making it easier to adjust the light source driving signal (PWM) to improve flicker.

11 and 12 are diagrams showing examples of driving signals of the backlight unit when the backlight unit is a direct type according to embodiments of the present invention.

Referring to FIG. 11, a plurality of light sources 500 may be disposed on a side of the backlight unit corresponding to the display panel 110. That is, the light source 500 can supply light in a direction perpendicular to the display panel 110.

While the display device 100 is driven in a low-speed driving mode, a light source driving signal (PWM) in which at least one of frequency, duty, and amplitude is varied during one frame period may be supplied.

For example, as shown in FIG. 11, the light source driving signal (PWM) with duty A% is supplied to the first subframe (SF1), and the light source driving signal (PWM) with duty A% is supplied to the second subframe (SF2) and the third subframe (SF2). A light source driving signal (PWM) with a duty of B% or C% may be supplied.

Additionally, the amplitude of the light source driving signal (PWM) supplied during each subframe period may vary.

Additionally, in some cases, the length of the subframe period or the delay period before the light source driving signal (PWM) is supplied in each frame period may vary.

At this time, in the direct backlight unit, each light source 500 is disposed on the surface corresponding to the display panel 110, so the light source 500 disposed in a certain area according to the image pattern receives the same light source driving signal (PWM). It may also be driven by

For example, as shown in FIG. 12, the light source 500 disposed in the fourth area (Area4) uses a light source driving signal (PWM) with a duty of A%, B%, and C% in each subframe period. ) can be driven by. Additionally, the light source 500 disposed in the fifth area (Area5) may be driven by a light source driving signal (PWM) having a duty of D%, E%, and F% in each subframe period. Here, the fourth area (Area4) and the fifth area (Area5), which are areas where light is emitted from one or more light sources 500, are determined according to the number, size, and shape of the areas according to the input image information. etc. may be set differently. For example, if the input image is divided into five areas and the light emitted must be controlled for each area, the areas where light is emitted from one or more light sources 500 may be divided into five areas of different sizes. It can be set to 1 area. In addition, the fourth area (Area4) and the fifth area (Area5), which are areas where light is emitted from one or more light sources 500, may be fixed or set differently for every frame of the display or for each frame. . For example, if the input image is an image that hardly changes for 30 frames, the set area may be set as a fixed area that does not change for 30 frames. Additionally, if the input image is an image that changes more than a predetermined standard every 10 frames, the set area can be set to change every 10 frames.

In this way, by independently controlling the light source driving signal (PWM) that drives the light source 500 that emits light in each area, the frequency component at which flicker is recognized according to the image pattern displayed in the low-speed driving mode is offset. The light source driving signal (PWM) can be easily adjusted.

In addition, in the direct backlight unit, each light source 500 can be driven independently, so at least one of the frequency, duty, amplitude, and delay period of the light source driving signal (PWM) is adjusted for each light source 500. By doing so, it is possible to facilitate control to avoid frequency components that generate flicker.

The above-described embodiments of the present invention reduce the frequency component that causes flicker among the frequency components of luminance that appears during the frame period by supplying a variable driving signal to the backlight unit in the low-speed driving mode of the display device 100. Make it possible to do it.

By reducing the frequency component that causes flicker, it is possible to prevent flicker from being recognized in low-speed driving mode.

Accordingly, power consumption can be reduced through the low-speed driving mode of the display device 100.

In addition, since flicker is prevented through frequency component analysis, driving efficiency of the display device 100 can be improved by enabling driving at a low display driving frequency with a longer frame period.

The above description is merely an illustrative explanation of the technical idea of the present invention, and various modifications and variations will be possible to those skilled in the art without departing from the essential characteristics of the present invention. In addition, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but rather to explain it, and therefore the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

100: display device 110: display panel
120: gate driving circuit 130: data driving circuit
140: Controller 200: Host system
300: operation circuit 400: driving circuit
500: light source 610, 620, 630: light source array

Claims (15)

display panel;
a backlight unit including a plurality of light sources and supplying light to the display panel; and
Includes a driving circuit that drives the plurality of light sources,
The driving circuit is,
Outputting at least one first light source driving signal and at least one second light source driving signal in one frame period while the display panel is driven in a low-speed driving mode,
The first light source driving signal and the second light source driving signal are different in at least one of frequency, duty, and amplitude,
The display device wherein the at least one first light source driving signal and the at least one second light source driving signal are aperiodic signals.

According to paragraph 1,
The first light source driving signal is output in a first subframe period of the one frame period, and the second light source driving signal is output in a second subframe period of the one frame period.
According to paragraph 1,
The first light source driving signal is output to a first light source among the plurality of light sources, and the second light source driving signal is output in a period corresponding to the subframe period in which the first light source driving signal is output to the first light source. 2 A display device that outputs light as a light source.
According to paragraph 1,
A display device wherein at least one of the first light source driving signal and the second light source driving signal is output multiple times in at least one subframe period among a plurality of subframe periods included in the one frame period.
According to paragraph 1,
A display device wherein the delay period of the light source driving signal output in the first frame period is different from the delay period of the light source driving signal output in the second frame period.
According to paragraph 1,
The plurality of light sources are disposed on at least one side of the backlight unit,
A display device in which the first light source driving signal and the second light source driving signal are output through different channels or output through the same channel during different subframe periods.
According to paragraph 1,
The plurality of light sources are disposed on a side of the backlight unit corresponding to the display panel,
The first light source driving signal and the second light source driving signal are output to light sources arranged in different areas, or are output to light sources arranged in the same area during different subframe periods.
According to paragraph 1,
The driving circuit is,
A display device that outputs a light source driving signal with constant frequency, duty, and amplitude in the one frame period while the display panel is driven in a normal driving mode.
According to paragraph 1,
Further comprising a controller transmitting light source control data to the driving circuit,
The controller is,
A display device that transmits different light source control data depending on at least one of a driving frequency of the low-speed driving mode and image data input to the controller.
display panel;
a backlight unit supplying light to the display panel; and
Including a plurality of light sources included in the backlight unit,
At least one of the plurality of light sources is,
In the first driving mode, the driving frequency, ratio of the emission period, emission luminance level and emission start timing are constant,
In the second driving mode, at least one of the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing is varied within the one frame,
The plurality of light sources include a first light source and a second light source,
The first light source and the second light source,
In the first driving mode, the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing are the same,
A display device in which at least one of the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing is different in the second driving mode.
delete According to clause 10,
At least one of the plurality of light sources is,
A display device that repeats light emission and non-light emission a plurality of times during at least one driving period according to the driving frequency in the second driving mode.
According to clause 10,
A display device wherein the driving frequency of the light source in the first driving mode is higher than the driving frequency of the light source in the second driving mode.
In a backlight unit including a plurality of light sources,
At least one of the plurality of light sources,
In the first driving mode, the driving frequency, the ratio of the emission period, the emission luminance level and the emission start timing are constant,
In the second driving mode, at least one of the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing is varied within the one frame,
The plurality of light sources include a first light source and a second light source,
The first light source and the second light source,
In the first driving mode, the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing are the same,
A backlight unit in which at least one of the driving frequency, the ratio of the light emission period, the light emission luminance level, and the light emission start timing is different in the second driving mode.
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